HIGH-RISK PREGNANCY

'At risk' approach is the most practical and cost-effective tool for antenatal care in resource-poor countries, which means 'Identification of high-risk mothers (Table 12.2) during antenatal period and arrange more skilled care for them, while continuing to provide appropriate care for other low-risk mothers'.

High-risk pregnancies are often at-risk to terminate into abortions, stillbirths, prematurity, IUGR and congenital malformations. Common indicators of high- risk pregnancies may be recognizable even before the conception and these case should be managed only at centers where adequate facilities for fetal monitoring, neonatal resuscitation and critical care of sick newborn are available.

TABLE 12.3: Effect of common maternal disorders and drug exposure on fetus and newborn

IUGR: Intrauterine growth retardation; ID: Intellectual disability; NTDs: Neural tube defects; TOF: Tracheoesophageal fistula; ITP: Immune thrombocytopenia; APH: Antepartum hemorrhage

¹Fetal alcohol syndrome: Facial dysmorphism, IUGR, developmental delay, learning/behavioral problems

²Fetal hydantoin syndrome: IUGR, facial dysmorphism, hypoplastic nails, mild MR

• USG assessment is most accurate method for dating gestation in normal fetus. Different fetal parameters are used in different stages of gestation—crown-heel length (up to 12 weeks), bi-parietal diameter (up to 28 weeks) and femoral length beyond this age.

II. Assessment of fetal growth by:

• Maternal weight gain: Steady maternal weight gain indicates satisfactory fetal growth. Average healthy Indian woman gains ~ 9-10 kg in pregnancy.

• Serial abdominal girth increase of ~1 cm/week from 20th week onwards, indicates normal fetal growth.

• Serial increase in UFH is a reliable indicator of adequate fetal growth, when compared with gestation-parto- graphs (fetal growth charts).

• USG assessment is a non-invasive and accurate tool to identify intrauterine growth retardation (IUGR) apart from other obstetrical abnormalities, e.g. multiple pregnancies, congenital anomalies, abnormal placental morphology, presence of poly/oligohydramnios, etc. A Bi-parietal diameter lt;8.5-9.0 cm at full term indicates IUGR. However, Fetal head/thorax or head/ abdomen ratio are more reliable, as somatic growth is more affected in IUGR.

III. Assessment of physiological maturity of fetus is indicated in expected preterm deliveries. It requires amniocentesis with following tests in amniotic fluid (AF):

• Lung surfactant maturity, e.g. L:S ratio (gt;2)

• Amniotic fluid optical density (gt; 0.15)

• Renal maturity (AF creatinine gt; 2 mg/dl)

• Skin maturity by AF cytology (gt; 20% orange staining cells).

IV. Detection of congenital anomalies is based on:

• Routine screening, e.g. USG or serology.

• Genetic studies, e.g. karyotyping in select cases.

• Amniotic fluid biochemistry:

- Raised a-fetoprotein levels (14-16 weeks) in neural tube defects, exomphalos, gut atresia.

- Raised optical density difference gt;0.1 in Rh-hemolytic disease with severe hemolysis.

- Raised pregnanediol levels in congenital adrenal hyperplasia

- Low human chorionic gonadotropin levels indicate threatened abortion; elevated levels in Down syn­drome and molar pregnancy.

- Specific enzyme assays in suspected IEMs.

#945;-fetoproteins (AFP) is a glycoprotein, produced by yolk sac and fetal liver from 2^nd months onwards.

Maternal or amniotic fluid AFP levels are useful biochemical markers of fetal well-being. Normally, maternal serum AFP is ~25 ng/ ml at 16^th week (optimal time for screening) and rises by ~15% per week till 30^th weeks, followed by gradual decline. AFP levels are elevated in neural tube defects, liver defects, some congenital malformations and multiple pregnancies, while reduced in Down syndrome.

V. Assessment for fetal distress: Although clinical monitoring of fetal heart sounds and movements is the simplest tool to assess fetal well-being, following evaluation may be necessary in selected cases to decide the need for immediate intervention:

a. Indicators of placental dysfunction (maternal sample)

- S. placental lactogen (lt;4 #956;g#8725;ml after 30 weeks)

- Plasma/urine estriol (gt;30% drop from earlier values)

b. Tests for uteroplacental unit:

- Non-stress monitoring (NST), i.e. simultaneous recording of Fetal heart rate (FHR), uterine contrac­tions and fetal movements. Acceleration of FHR by gt;15 bpm or for gt;15 seconds after fetal movement, at least twice in 20 minutes, indicates adequate utero-placental function.

- Oxytocin challenge test to assess effect of oxytocin stimulated uterine contractions on FHR. Persistent slowing of FHR after uterine contraction (late deceleration) indicates placental insufficiency.

c. Direct indicators of fetal distress:

- Fetal heart monitoring (absent FHS)

- Fetal activity record (less/absent movements)

- Fetal biophysical profile (USG based)

- Fetal scalp blood sampling for blood gas analysis Fetal biophysical profile is the most accurate non- invasive test for fetal well-being, using five USG-based fetal parameters—(i) posture, (ii) breathing movements, (iii) gross body movements, (iv) reactive heart rate and (v) volume of amniotic fluid. Each parameters is scored as 2 normal or 0 as abnormal. A combined score of 6 or less indicates chronic fetal asphyxia.

Fetal scalp blood sampling for blood gas analysis under endoscopic guidance, is most reliable but invasive test. A scalp pH of lt;7.1 indicates severe hypoxia and need for immediate delivery.

12.3.4